default or selected kernelversion does not have config value CONFIG_FB_IMAC.
Result is shown for kernelversion 5.3.7
Intel-based Macintosh Framebuffer Support
modulename: imacfb.ko
configname: CONFIG_FB_IMAC
Linux Kernel Configuration
└─>Device Drivers
└─>Graphics support
└─>Support for frame buffer devices
└─>Intel-based Macintosh Framebuffer Support
In linux kernel since version 2.6.20 (release Date: 2007-02-04)
This is the frame buffer device driver for the Intel-based Macintosh